aid: steel-dev
name: Steel
review:
  question: Does Steel expose a documented public WebSocket API?
  answer: true
  date: '2026-06-20'
  reviewer: API Evangelist
  asyncapiSpecCreated: false
  asyncapiScopeNote: |
    Steel exposes a real, documented WebSocket surface: a per-session Chrome
    DevTools Protocol (CDP) endpoint returned as `websocketUrl` (wss://) from
    the Sessions API. However, this WebSocket speaks the Chrome DevTools
    Protocol, a vendor JSON-RPC wire protocol designed to be driven by
    Playwright / Puppeteer / Selenium client libraries rather than a
    Steel-authored, channel-and-message-documented API. Steel does not publish
    a message/channel catalog for this socket; the contract is CDP itself. An
    AsyncAPI document was therefore NOT authored, because faithfully modeling
    it would mean re-modeling the entire Chrome DevTools Protocol, which is not
    a Steel interface. The WebSocket connect surface is instead documented in
    this review and surfaced as the steel-dev:steel-browser-connect-api entry
    in apis.yml.
findings:
  summary: |
    Steel publishes a documented public WebSocket surface, but it is a
    transport for the Chrome DevTools Protocol rather than a bespoke Steel
    message API. Every browser session created via POST /v1/sessions returns a
    `websocketUrl` (wss://) which clients connect to with
    browser.connect_over_cdp() (Playwright), puppeteer.connect() (Puppeteer),
    or a Selenium grid binding. The rest of the Steel surface is REST/HTTPS
    under https://api.steel.dev/v1 (self-hosted default http://localhost:3000/v1),
    authenticated with the Steel-Api-Key header. Steel is open source under
    Apache-2.0 (github.com/steel-dev/steel-browser); the same routes run
    self-hosted.
  transports:
    - protocol: REST
      scheme: https
      baseURL: https://api.steel.dev/v1
      documented: true
    - protocol: WebSocket
      scheme: wss
      note: >-
        Per-session CDP WebSocket returned as session.websocketUrl. Speaks the
        Chrome DevTools Protocol (JSON-RPC), driven by Playwright / Puppeteer /
        Selenium. Documented as a connect target, not as a Steel-authored
        channel/message catalog.
      documented: true
  endpointsConfirmedRest:
    - POST   https://api.steel.dev/v1/sessions
    - GET    https://api.steel.dev/v1/sessions
    - GET    https://api.steel.dev/v1/sessions/{sessionId}
    - GET    https://api.steel.dev/v1/sessions/{sessionId}/context
    - GET    https://api.steel.dev/v1/sessions/{sessionId}/live-details
    - POST   https://api.steel.dev/v1/sessions/{sessionId}/release
    - POST   https://api.steel.dev/v1/sessions/release
    - POST   https://api.steel.dev/v1/sessions/scrape
    - POST   https://api.steel.dev/v1/sessions/screenshot
    - POST   https://api.steel.dev/v1/sessions/pdf
    - POST   https://api.steel.dev/v1/scrape
    - POST   https://api.steel.dev/v1/screenshot
    - POST   https://api.steel.dev/v1/pdf
    - POST   https://api.steel.dev/v1/search
    - GET    https://api.steel.dev/v1/sessions/{sessionId}/files
    - POST   https://api.steel.dev/v1/sessions/{sessionId}/files
    - DELETE https://api.steel.dev/v1/sessions/{sessionId}/files
  websocketConfirmed:
    - wss://connect.steel.dev session CDP endpoint (session.websocketUrl), connect via Playwright connect_over_cdp / Puppeteer connect / Selenium.
sources:
  - url: https://docs.steel.dev/api-reference
    type: APIReference
    note: REST endpoints under https://api.steel.dev/v1 with the Steel-Api-Key header.
  - url: https://docs.steel.dev/overview/sessions-api
    type: Documentation
    note: Sessions return websocketUrl, debugUrl, sessionViewerUrl; live viewer documented.
  - url: https://docs.steel.dev/overview/guides/connect-with-playwright
    type: Documentation
    note: Connect to the session CDP WebSocket with Playwright connect_over_cdp.
  - url: https://github.com/steel-dev/steel-browser
    type: SourceCode
    note: Apache-2.0 open-source server; routes for sessions, scrape, screenshot, pdf, search, files, and CDP/Selenium connect.
actions:
  asyncapiPath: null
  apisYmlUpdated: true
  reason: |
    The documented WebSocket is a CDP transport, not a Steel-authored
    message/channel API, so no AsyncAPI document was created. The CDP /
    browser-connect surface is instead represented as a dedicated API entry
    (steel-dev:steel-browser-connect-api) in apis.yml and documented in detail
    in this review, with the OpenAPI noting websocketUrl on session responses.
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com